Beautiful New Year weather here, so I took the opportunity to clean the engine bay in preparation for maintenance work (heater matrix, cleaning MAF, plugs, etc).

I came back on an old problem, which is a short (max. ~1 sec) rasping noise if I blip the engine.
No hissing or other noise if idling.

I first thought vacuum line, but can't find anything loose.
Then thought the VVT, but disconnecting them does not change anything.
Finally, checked the plugs and fuel injectors, but nothing there.

If I try to pin down the location, it rally looks like it come right from the middle of the intake manifold.

Not sure what is under that.
All I know I noticed this sound 2 years ago for a while.
Since then, the manifold has been off to change cooling hoses, and I presume new seals / gaskets have been used on installation.

Really wonder if anyone can point me to anything to trace furhter.

Thanks, and Happy New Year,

Eric

 

Beneath the manifold are a water hose that runs front to rear of the engine and the knock sensors, not much else. My guess at what you are hearing might be a leak in the EGR valve piping. See attached. It is just a stab at it, but a place to start.

 

My rasping noise when blipping the throttle or running through the gears, turned out to be a loose baffle in the first muffler. Replacing it fixed the problem.

 

Both suggestions well noted.

I first fixed a very dirty MAF last week, resulting in all fuel trims back to normal.
Did however not have time any more to dig any deeper on this matter, as I am on a 2 week trip.
Will surely pursue this further once back on the island.

Thanks again!

Eric